Control of abnormal pressure to hydrocarbon migration accumulation - A Case Study on the lower assemblage of Yanchang formation in the middle area of western Ordos Basin

摘要

In this article the author use the datas of acoustic travel time, systematical analysising the abnormal pressure distribution obtained by equilibrium depth method in the lower assemblage of Yanchang formation 151 well bores in the middle area of western Ordos Basin, combined with the distribution patterns of hydrocarbon reservoir discovered in the researched region, the relationship between abnormal pressure and distributions of hydrocarbon reservoir discovered and also hydrocarbon migration & accumulation is disclosured. The study shows that the abnormal pressure is presented in each well of Chang 7 and Chang 8 oil-bearing formation in the researched region. The difference of abnormal pressure between Chang 7 and Chang 8, usually about 8 ~ 12MPa, is the principal dynamic power to make the migration of hydrocarbon downward. The hydrocarbon reservoir discovered is closely relative with the abnormal pressure, most of hydrocarbon reservoirs distribute in areas with high abnormal pressure difference on a background of low abnormal pressure difference between Chang 7 and Chang 8.